# If (-8,4),(2,4)and(5,a) collinear point then find the value of a

2
by parthoooooooo

2014-08-11T14:03:05+05:30
A= 4

three points are said to be collinear, if they all lie in straight line..
also, the slope should be same..

slope = (y2-y1) / (x2-x1)

so, for eg., say if a= (-8,4) , b= (2,4) and c=(5,a)

ab = (4-4)/(2-4) = 0/-2 = 0

bc = (a-4/5-2) = (a-4)/3 = 0 (since slope is "0" for ab)
(a-4) = 0
a = 4

ac = (a-4)/(5+8) = 0 (since slope is "0" for ab)
a-4/13 = 0
a-4 = 0
a = 4

2014-08-15T09:07:19+05:30
Three points are said to be collinear, if they all lie in straight line..
slope of the line passing through the points is given by

slope = (y2-y1) / (x2-x1)

let us take the points  a= (-8,4) , b= (2,4) and c=(5,a)
first finding the slope of the line passing through a and b

ab = (4-4)/(2-4)
= 0/-2
= 0
next finding the slope of the line passing through the points b and c

bc = (a-4/5-2) =
(a-4)/3
= 0 (since slope is "0" for ab)
so we have
(a-4) = 0
a = 4        (Adding 4 on both sides)
slope of the line passing through the points a and c is

ac = (a-4)/(5+8) = 0 (since slope is "0" for ab)
a-4/13 = 0
a-4 = 0
a = 4